System and method for controlling coolant flow through a heater core of a vehicle based on a temperature of air in a duct that supplies air to a passenger cabin of the vehicle

ABSTRACT

A system includes a temperature error module and a coolant flow control module. The temperature error module determines an error between a target air temperature and a measured air temperature of a duct that supplies air to a cabin of a vehicle. The coolant flow control module controls a rate at which coolant flows to a heater core of the vehicle by adjusting at least one of a position of a coolant control valve of the vehicle and an output of an electric coolant pump of the vehicle. The coolant flow control module also controls the coolant flow rate to decrease the error between the target air temperature and the measured air temperature.

INTRODUCTION

The information provided in this section is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

The present disclosure relates to systems and methods for controlling coolant flow through a heater core of a vehicle based on a temperature of air in a duct that supplies air to a passenger cabin of the vehicle.

Engine cooling systems typically include a coolant pump and may include a coolant control valve. The coolant pump circulates coolant through a cooling system for an engine. The coolant control valve directs the coolant to different components of the system. The components to which coolant is directed typically include a radiator, a heater core, a transmission fluid heat exchanger, and an engine oil heat exchanger.

The heater core is used to heat air flowing to the passenger cabin of the vehicle, and thereby maintain the temperature of air in the passenger cabin at a comfortable temperature for occupants of the vehicle. Heat is transferred from coolant circulating through the heater core to air passing through the heater core before the air enters the passenger cabin. Typically, a blower is used to force the air through the heater core and into a duct that supplies air to the passenger cabin.

SUMMARY

A system according to the present disclosure includes a temperature error module and a coolant flow control module. The temperature error module determines an error between a target air temperature and a measured air temperature of a duct that supplies air to a cabin of a vehicle. The coolant flow control module controls a rate at which coolant flows to a heater core of the vehicle by adjusting at least one of a position of a coolant control valve of the vehicle and an output of an electric coolant pump of the vehicle. The coolant flow control module also controls the coolant flow rate to decrease the error between the target air temperature and the measured air temperature.

In one aspect, the coolant flow control module determines whether to adjust the coolant flow rate to decease the error based on at least one of an opening amount of a heater flap that regulates airflow to the heater core and a magnitude of the error.

In another aspect, the coolant flow control module adjusts the coolant flow rate to decrease the error when the magnitude of the error is greater than a predetermined value.

In another aspect, the coolant flow control module adjusts the coolant flow rate to decrease the error when the opening amount of the heater core is greater than a predetermined amount.

In another aspect, the coolant flow control module adjusts the coolant flow rate independent of the error when at least one of the opening amount of the heater flap and the magnitude of the error satisfies a predetermined criteria.

In another aspect, the coolant flow control module adjusts the coolant flow rate independent of the error when the magnitude of the error is less than a predetermined value.

In another aspect, the coolant flow control module adjusts the coolant flow rate independent of the error when the opening amount of the heater flap is less than a predetermined amount.

In another aspect, the coolant flow control module adjusts the coolant flow rate independent of the error by decreasing the coolant flow rate at a predetermined rate.

In another aspect, the coolant flow control module stops decreasing coolant flow when at least one of the magnitude of the error is greater than a predetermined value and the opening amount of the heater flap is greater than a predetermined amount.

In another aspect, the coolant flow control module determines a target flow rate based on the error, a flow rate of air passing through the duct, a temperature of air in the duct, and a coolant temperature. The coolant flow control module also adjusts at least one of the position of the coolant control valve and the output of the electric coolant pump to minimize a difference between the coolant flow rate and the target flow rate.

A method according to the present disclosure includes determining an error between a target air temperature and a measured air temperature of a duct that supplies air to a cabin of a vehicle. The method further includes controlling a rate at which coolant flows to a heater core of the vehicle by adjusting at least one of a position of a coolant control valve of the vehicle and an output of an electric coolant pump of the vehicle. The method further includes controlling the coolant flow rate to decrease the error between the target air temperature and the measured air temperature.

In one aspect, the method further includes determining whether to adjust the coolant flow rate to decrease the error based on at least one of an opening amount of a heater flap that regulates airflow to the eater core and a magnitude of the error.

In another aspect, the method further includes adjusting the coolant flow rate to decrease the error when the magnitude of the error is greater than a predetermined value.

In another aspect, the method further includes adjusting the coolant flow rather independent of the error when at least one of the opening amount of the heater flap and the magnitude of the error satisfies a predetermined criteria.

In another aspect, the method further includes adjusting the coolant flow rate independent of the error when the magnitude of the error is less than a predetermined value.

In another aspect, the method further includes adjusting the coolant flow rate independent of the error when the opening amount of the heater flap is less than a predetermined amount.

In another aspect, the method further includes adjusting the coolant flow rate independent of the error by decreasing the coolant flow rate at a predetermined rate.

In another aspect, the method further includes stopping decreasing coolant flow when at least one of the magnitude of the error is greater than a predetermined value and the opening amount of the heater flap is greater than a predetermined amount.

In another aspect, the method further includes determining a target flow rate based on the error, a flow rate of air passing through the duct, a temperature of air in the duct, and a coolant temperature. The method further includes adjusting at least one of the position of the coolant control valve and the output of the electric coolant pump to minimize a difference between the coolant flow rate and the target flow rate.

Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of an example vehicle system including a control module according to the principles of the present disclosure;

FIG. 2 is a functional block diagram of the control module of FIG. 1;

FIGS. 3A-3C are flowcharts illustrating an example control method according to the principles of the present disclosure;

FIG. 4 is a graph illustrating an example control method according to the principles of the present disclosure; and

FIG. 5 is a graph illustrating the effect of an example control method according to the principles of the present disclosure.

In the drawings, reference numbers may be reused to identify similar and/or identical elements.

DETAILED DESCRIPTION

As discussed above, engine cooling systems circulate coolant to transfer heat generated by an engine to other parts of the cooling system, such as a heater core and a radiator. Coolant is circulated by a coolant pump, and the rate at which coolant is circulated through the cooling system is controlled by adjusting the output of the coolant pump and/or the position a coolant control valve (if present). In addition, the position of the coolant control valve may be adjusted to control the rate of coolant flow to a particular component of the cooling system. In vehicles that are not equipped with an automatic engine start-stop system, only one coolant pump is typically used to circulate coolant through the coolant system, and the coolant pump is typically driven by the engine (i.e., mechanically driven). Thus, the speed of the engine, hydraulic restrictions, and engine coolant temperature dictate the maximum rate at which coolant is circulated through the cooling system.

In vehicles that are equipped with an automatic engine start-stop system, multiple coolant pumps are typically used to circulate coolant through the cooling system. The coolant pumps include a primary coolant pump that is mechanically driven, and an auxiliary coolant pump that is electrically driven. In some cases, operation of the auxiliary coolant pump is enabled based on an error between a measured temperature of air in a duct that supplies air to a passenger cabin of a vehicle and a target air temperature that is set by a vehicle occupant. More specifically, the auxiliary coolant pump is started (i.e., turned on) when the error exceeds a threshold value and stopped (i.e., turned off) when the error no longer exceeds the threshold value. When the auxiliary coolant pump is started, the auxiliary coolant pump is operated at a fixed capacity (i.e., independent of the error).

In some vehicles equipped with an automatic engine start-stop system, the primary coolant pump is electrically driven and is the only coolant pump in the cooling system. In these vehicles, the primary coolant pump is operated when the engine is running. The primary coolant pump is also operated when the engine is automatically stopped (i.e., stopped independent of an ignition system of the engine) in order to circulate coolant through a heater core.

Regardless of whether a vehicle is equipped with an electrically-driven and/or mechanically-driven coolant pump, the flow rate of coolant circulated through the heater core is typically controlled based on the temperature of the coolant. The flow rate of coolant may be controlled based on other factors in addition to temperature of the coolant, such as engine speed and hydraulic restrictions. The coolant flow rate is generally increased as the coolant temperature increases in order to provide additional cooling to the engine. Thus, when the coolant temperature is greater than or equal to its normal operating temperature, the coolant flow rate is set to at or near its maximum value.

In order to control the temperature of the air supplied to the passenger cabin, coolant is circulated through the heater core as discussed above, and a heater flap or door is adjusted to vary the amount of air that passes through the heater core. Since the coolant flow rate is generally increased as the coolant temperature increases, the coolant circulating through the heater core may supply more heat than necessary to maintain the cabin air temperature at a target temperature. Thus, the heater flap may be at least partially closed to decrease the amount of airflow through the heater core.

Controlling the coolant flow rate based on the coolant temperature as described above ignores the ability of the cooling system to satisfy cabin heating demands by increasing airflow through the heater core instead of relying on excess coolant flow through the heater. In other words, controlling the coolant flow rate based on the coolant temperature as described above ignores the heat capacity of the cooling system to satisfy cabin heating demands at a lower coolant flow rate. In addition, circulating coolant through the heater core at a rate that is greater than the rate necessary to maintain the cabin air temperature at a target temperature may overcool the engine. Overcooling an engine causes the combustion temperature of the engine to decrease, which degrades fuel economy and engine performance (e.g., horsepower, torque). In addition, lower combustion temperatures resulting from overcooling may increase the amount of emissions produced by the engine.

A control system according to the present disclosure adjusts coolant flow to the heater core based on the error between the cabin air temperature and the target temperature. The system adjusts the coolant flow to minimize the error when the error is greater than or equal to a predetermined value. In an effort to optimize coolant flow through the heater core, when error is less than the predetermined value, the system decreases the coolant flow in small increments and increases the opening percentage of the heater flap to send more air through the heater core in order to compensate for the decrease in coolant flow. When the opening percentage of the heater flap reaches a predetermined value at or near a maximum or fully open position, the system stops decreasing the coolant flow, and once again controls the coolant flow based on the error. In this manner, the system maximizes the opening percentage of the heater flap to maximize airflow through the heater core before maximizing coolant flow.

By controlling the coolant flow through the heater core in the manner described above, the system minimizes the coolant flow through the heater core while maintaining the cabin air temperature at or near the target temperature. Minimizing coolant flow through the heater core avoids overcooling the engine, and thereby maintains combustion temperatures at a desired temperature. As a result, the system improves fuel economy, improves engine performance, and reduces emissions while maintaining cabin comfort.

Referring to FIG. 1, an example vehicle system 10 includes a duct 12 that supplies heated or cooled air to a cabin 14 of a vehicle. The cabin 14 includes a user interface device 16, such as a touchscreen or a button, which allows an occupant to select a target air temperature T_(T) for the cabin 14 to increase his or her comfort in a given environment. A user may directly set the target air temperature T_(T) by selecting a specific temperature. Alternatively, the user may select a heating or cooling level, such as “full heat,” and a vehicle control module (VCM) 17 may set the target air temperature T_(T) based on a predetermined relationship between the target air temperature T_(T) and the heating or cooling level. In this way, the user may indirectly set the target air temperature T_(T) by selecting the heating or cooling level.

An engine 18 combusts air and fuel in a combustion chamber of a cylinder to generate drive torque. For example, during combustion, a piston may reciprocate within the cylinder to generate the drive torque. Engine oil is used to lubricate the moving piston and other moving parts in the engine 18.

A cooling system 19 circulates coolant through various portions of the engine 18, such as a cylinder head, an engine block, and an integrated exhaust manifold. Generally, the cooling system 19 is used to absorb heat from the engine, the transmission, and other components, and to transfer the heat to air. For example, the cooling system 19 may circulate coolant through an engine oil heat exchanger (not shown) and/or a transmission heat exchanger (not shown) to absorb heat from the engine oil and/or the transmission fluid, respectively.

In the example shown, the cooling system 19 includes a coolant temperature sensor 20, a coolant pump 22, a coolant control valve 24, a heater core 26, and coolant lines 27. The cooling system 19 may also include a radiator (not shown), the engine oil heat exchanger, and/or the transmission fluid heat exchanger. The coolant lines 27 include an engine inlet line 27-1, an engine outlet line 27-2, a heater core inlet line 27-3, a heater core outlet line 27-4, and a heater core bypass line 27-5.

The coolant temperature sensor 20 measures a temperature T_(C) of a coolant circulated through the engine 18. The coolant temperature sensor 20 may include one or more temperature sensors disposed in the engine inlet line 27-1, the engine outlet line 27-2, the heater core inlet line 27-3, and/or the heater core outlet line 27-4. In the example shown, the coolant temperature sensor 20 is disposed in the engine outlet line 27-2 near the outlet of the engine 18.

The coolant pump 22 may be electrically-driven and is disposed downstream of the engine 18 and upstream of the heater core 26. When the coolant pump 22 is on, it circulates coolant through the engine 18, the heater core 26, and the coolant lines 27. The coolant pump 22 also circulates coolant through the radiator, the engine oil heat exchanger, and the transmission fluid heat exchanger if these components are included in the cooling system 19.

The coolant control valve 24 regulates the rate of coolant flow to various components of the cooling system 19 such as the radiator, the heater core 26, the transmission fluid heat exchanger, and/or the engine oil heat exchanger. The coolant control valve 24 also controls whether coolant is allow to flow to these components. The coolant control valve 24 may include a multiple input, multiple output valve or one or more other suitable valves. In various implementations, the coolant control valve 24 may be partitioned and have two or more separate chambers.

The coolant control valve 24 may bypass the heater core 26 when one or more operating conditions of the vehicle system 10 satisfy predetermined criteria. For example, the coolant control valve 24 may bypass the heater core 26 when there is no heating demand. The coolant control valve 24 may bypass the heater core 26 by preventing coolant flow from the heater core outlet line 27-4 to the engine inlet line 27-1. In turn, coolant may flow through the heater core bypass line 27-5 instead of flowing through the heater core 26. The coolant control valve 24 may prevent flow from the heater core inlet line 27-3 to the heater core bypass line 27-5 when the coolant control valve 24 is not bypassing the heater core 26.

In various implementations, the coolant control valve 24 may be located at the junction between the heater core inlet line 27-3 and the heater core bypass line 27-5. In these implementations, the coolant control valve 24 may bypass the heater core 26 by preventing coolant flow from the coolant pump 22 to the heater core inlet line 27-3. In addition, the coolant control valve 24 may allow coolant flow through the heater core bypass line 27-5 when bypassing the heater core 26, and otherwise prevent coolant flow through the heater core bypass line 27-5.

The heater core 26 is a heat exchanger that transfers heat from engine coolant to air passing through the heater core 26. The heater core 26 is disposed in the duct 12. The heater core 26 receives air 28 from, for example, an engine compartment (not shown). More specifically, a blower 30 directs the air 28 to the heater core 26 through the duct 12.

A heater flap or door 32 is disposed in the duct 12 and regulates the flow of air from the blower 30 to the heater core 26. The heater flap 32 may include a plate or door and an actuator, such as a solenoid, that adjusts the position of the plate to adjust the opening percentage of the heater flap 32. The heater flap 32 allows more air to pass through the heater core when the opening percentage of the heater flap 32 is increased and vice versa.

An inlet air temperature sensor 34 is disposed in the duct 12 upstream of the heater core 26. An outlet air temperature sensor 36 and an air flow meter 38 are disposed in the duct 12 downstream of the heater core 26. The outlet air temperature sensor 36 measures a temperature T_(AO) of air in the duct 12 (i.e., the temperature of air supplied to the cabin 14). The air flow meter 38 measures a flow rate F_(A) of air in the duct 12 (i.e., the flow rate of air entering the cabin 14 through the duct 12). In various implementations, the duct air flow rate F_(A) may be estimated based on, for example, the speed of the blower 30, the position of the heater flap 32, and the position of a mode door that directs air through vents to the cabin. In these implementations, the air flow meter 38 may be omitted.

Outputs of the user interface device 16, the coolant temperature sensor 20, the inlet air temperature sensor 34, and the outlet air temperature sensor 36 may be inputs to the VCM 17. Another input to the VCM 17 may be the duct air flow rate F_(A) which, as discussed above, may be measured by the air flow meter 38 or estimated. In response to the inputs, the VCM 17 controls the engine 18, the coolant pump 22, the coolant control valve 24, the blower 30, and the heater flap 32. The VCM 17 controls the coolant control valve 24 and/or the coolant pump 22 to minimize the flow of coolant through the heater core 26 while maintaining the duct air temperature T_(AO) at a target air temperature.

Referring now to FIG. 2, an example implementation of the VCM 17 includes a coolant flow control module 42, a temperature error module 44, and a heater flap control module 46. The temperature error module 44 determines a duct temperature error E, which is the difference between the target air temperature T_(T) and the duct air temperature T_(AO) measured by the outlet air temperature sensor 36. The temperature error module 44 determines the target air temperature T_(T) based on an input from the user interface device 16. The temperature error module 44 receives the duct air temperature T_(AO) from the outlet air temperature sensor 36. The error E is used by the coolant flow control module 42 to determine a target coolant flow rate F_(C).

The heater flap control module 46 controls the amount of air that passes from the blower 30 through the heater flap 32 to the heater core 26. The heater flap control module 46 controls an opening amount (e.g., opening percentage) H of the heater flap 32 based on an input from the user interface device 16 and/or the duct air temperature T_(AO) from the outlet air temperature sensor 36. Thus, the heater flap control module 46 increases the heater flap opening amount H to meet a higher heating demand.

The coolant flow control module 42 controls coolant flow to meet an occupant heating demand. The coolant flow control module 42 controls coolant flow in a primary control mode or a secondary control mode. In the primary control mode, the coolant flow control module 42 controls the coolant flow based on the error E between the target air temperature T_(T) and the measured temperature T_(AO) of the air duct 12. In the secondary control mode, the coolant flow control module 42 controls the coolant flow based on the opening amount H of the heater flap 32.

The coolant flow control module 42 determines whether a heating request is present based on a user input from the user interface device 16, the status of a propulsion system (e.g., whether the engine 18 is running), the speed B of the blower 30, the opening amount H of the heater flap 32, and the coolant temperature T_(C) from the coolant temperature sensor 20. If all of these inputs satisfy conditions for a heating request to be present, the coolant flow control module 42 determines whether to operate in the primary control mode or the secondary control mode. Otherwise, the coolant flow control module 42 may set the coolant flow rate F_(C) to zero. In one example, the coolant flow control module 42 determines that a heating request is present when the user selects a target air temperature that is greater than the duct air temperature T_(AO) from the outlet air temperature sensor 36, the engine 18 is running, the blower speed B is greater than a predetermined speed, the opening amount H of the heater flap 32 is greater than a predetermined amount, and the coolant temperature T_(C) is greater than a predetermined temperature.

The coolant flow control module 42 enters the primary control mode when the opening amount H of the heater flap 32 is greater than or equal to a predetermined heater flap opening amount H₁. Until the predetermined heater flap opening amount H₁ is reached, the heater flap control module 46 is allowed to increase the heater flap opening amount H to meet the occupant heating demand (to minimize the error E) while maintaining a constant coolant flow rate.

When the predetermined heater flap opening amount H₁ is met, the coolant flow control module 42 enters the primary control mode. In the primary control mode, the coolant flow control module 42 adjusts the coolant flow based on the duct air temperature error E and independent of the opening amount H of the heater flap 32. More specifically, the coolant flow control module 42 adjusts the coolant flow to minimize the duct air temperature error E. In this regard, the coolant flow control module 42 controls the duct air temperature T_(AO) in a closed loop manner by adjusting the coolant flow to minimize the error E. The coolant flow control module 42 adjusts the coolant flow by adjusting the output of the coolant pump 22 and/or the position of the coolant control valve 24. The coolant flow control module 42 continues to control the coolant flow in a closed loop manner while monitoring the error E. When the error E is less than a predetermined value E₁₋₂ and the opening amount H of the heater flap 32 is less than a predetermined heater flap opening amount H₂, the coolant flow control module 42 enters the secondary control mode.

In the secondary control mode, the coolant flow control module 42 incrementally decreases coolant flow by a predetermined flow increment F_(i) and/or at a predetermined rate. As the coolant flow control module 42 decreases coolant flow, the heater flap control module 46 increases the heater flap opening amount H to meet the occupant heating demand. More specifically, the error E increases as the coolant flow control module 42 decreases coolant flow and, in response to the increase in the error E, the heater flap control module 46 increases the heater flap opening amount H to decrease the error E. The coolant flow control module 42 continues to incrementally decrease the coolant flow by F_(i) until the coolant flow control module 42 exits the secondary control mode.

The coolant flow control module 42 exits the secondary control mode and enters the primary control mode when the error E exceeds the predetermined error E₁₋₂ and/or the heater flap opening amount H exceeds the predetermined opening amount H₂. When the heater flap opening amount H exceeds the predetermined heater flap opening amount H₂, no additional heating capacity is available via the heater flap 32. Thus, the coolant flow control module 42 must increase coolant flow to meet a heating demand. When the error E exceeds the predetermined error E₁₋₂, the coolant flow control module 42 increases the coolant flow to meet the heating demand. Thus, the coolant flow control module 42 returns to the primary control mode to increase coolant flow to meet the occupant heating demand and minimize the error E when at least one of the exit conditions is met.

With reference to FIGS. 3A-3C and 4, an example method for controlling coolant flow begins at 60. The method is described in the context of the modules included in the example implementation of the VCM 17 shown in FIG. 2. However, the particular modules that perform the steps of the method may be different than those mentioned below and/or the method may be implemented apart from the modules of FIG. 2.

The method is further discussed in the context of an example graph shown in FIG. 4. The graph includes an x-axis 50 and a y-axis 51. The graph shows a target air temperature 52, a measured duct air temperature 54, a heater flap opening amount 56, and an actual coolant flow rate 58. The x-axis 50 represents time, and the period represented by the x-axis may be on the order of minutes. The y-axis 51 represents the magnitudes of the target air temperature 52, the measured duct air temperature 54, the heater flap opening amount 56, and the coolant flow rate 58.

Returning to FIG. 3A, at 62, the coolant flow control module 42 determines whether cabin heating is active. Cabin heating can be detected when the user interface device 16 is set above full cold. For example, the user interface device 16 may be set to heat the vehicle cabin 14 to a certain temperature or to a temperature level. If cabin heating is active, the method continues at 66. Otherwise, the method remains at 62 and continues to determine whether cabin heating is active.

At 66, the coolant flow control module 42 determines whether a propulsion system is active (e.g., whether the engine 18 is running). If the propulsion system is active, the method continues at 68. Otherwise, the method returns to 62.

At 68, the coolant flow control module 42 determines whether the speed B of the blower 30 is greater than or equal to a predetermined speed B₀ or threshold. The predetermined blower speed B₀ may correspond to a power of 10-15%, for example, to ensure that there is sufficient airflow through the duct 12 prior to circulating coolant. If the blower speed B is greater than or equal to the predetermined speed B₀, the method continues at 70. Otherwise, the method returns to 62.

At 70, the coolant flow control module 42 determines whether the heater flap opening amount 56 is greater than or equal to a predetermined opening amount 72 (FIG. 4). The predetermined opening amount 72 may be 30%. If the heater flap opening amount 56 is greater than or equal to the predetermined opening amount 72, the method continues at 74. Otherwise, the method returns to 62.

At 74, the coolant flow control module 42 receives the coolant temperature T_(C) from the coolant temperature sensor 20. At 76, the coolant flow control module 42 determines whether the coolant temperature T_(C) is greater than or equal to a predetermined coolant temperature 80. This step ensures that cold coolant is not circulated through the heater core 26. Circulating cold coolant through the heater core 26 could result in cool air passing to the cabin 14. If the coolant temperature T_(C) is greater than or equal to the predetermined coolant temperature 80, the method continues at 77 (FIG. 3B). Otherwise, the method returns to 62.

Referring to FIG. 3B, a method for controlling coolant flow in the primary control mode begins at 77. At 78, the coolant flow control module 42 determines whether the heater flap opening amount 56 is greater than a predetermined opening amount 106 (FIG. 4). The predetermined opening amount 106 may be about 60%.

If the heater flap opening amount 56 is greater than the predetermined opening amount 106, the method continues at 82. Otherwise, the method returns to 78. Thus, the coolant flow control module 42 does not control coolant flow based on the duct air temperature T_(AO) until the heater flap opening amount 56 reaches the predetermined opening amount 106. This step prevents increasing coolant flow when the heater flap 32 has additional capacity to provide air to the heater core 26.

At 82, the coolant flow control module 42 receives a duct air temperature T_(AO) from the outlet air temperature sensor 36. At 84, the temperature error module 44 calculates an error 86 (FIG. 4) based on the duct air temperature T_(AO) and the target air temperature 52. The temperature error module 44 calculates the error 86 using an equation such as

E=T _(T) −T _(AO),  (1)

where E represents the error 86, T_(T) represents the target air temperature 52, and T_(AO) represents the measured duct air temperature 54.

At 88, the coolant flow control module 42 determines whether the error 86 is greater than a predetermined error 90. The predetermined error 90 may be about 2%. If the error 86 is greater than the predetermined error 90, the method continues at 91 (FIG. 3C). Otherwise, the method continues at 94.

At 94, the coolant flow control module 42 receives the duct air flow rate F_(A), either from the air flow meter 38 or estimated. Alternatively, the coolant flow control module 42 may estimate the duct air flow rate F_(A) based on, for example, the speed of the blower 30, the position of the heater flap 32, and the position of the mode door that directs air through vents to the cabin. At 96, the coolant flow control module 42 receives the inlet air temperature T_(AI) from the inlet air temperature sensor 34. At 98, the coolant flow control module 42 receives the coolant temperature T_(C) from the coolant temperature sensor 20. At 100, the coolant flow control module 42 looks up or retrieves a stored value of a specific heat of air C_(P-A) at the inlet at temperature T_(AI). The coolant flow control module 42 also looks up or retrieves a stored value of a specific heat of coolant C_(P-C) at the coolant temperature T_(C).

At 102, the coolant flow control module 42 determines the target coolant flow rate F_(C) based the error 86, the duct air flow rate F_(A), the specific heat of air C_(PA) at the inlet temperature T_(AI), and the specific heat of coolant C_(P-C) at the coolant temperature T_(C). The target coolant flow rate F_(C) is calculated using equations such as

$\begin{matrix} {P = {F_{A}C_{P - A}E}} & (2) \\ {F_{C} = \frac{P}{C_{P - C}K}} & (3) \\ {F_{C} = \frac{F_{A}C_{P - A}E}{C_{P - C}K}} & (4) \end{matrix}$

where P is the cabin heat load power in steady-state conditions and K is a calibration factor that represents expected temperature drop across the heater core 26 for a given heater load. The cabin heat load power P of Equation (2) is plugged into Equation (3) to derive Equation (4). At 104, the coolant flow control module 42 adjusts the output of the coolant pump 22 and/or the position of the coolant control valve 24 to provide the target coolant flow rate F_(C) to the heater core 26. The coolant flow control module 42 may accomplish this using, for example, a function or mapping that relates target coolant flow rate to coolant pump output and/or coolant control valve position. The method then returns to 82.

Referring now to FIG. 3C, a method for controlling coolant flow in the secondary control mode begins at 91. At 92, the coolant flow control module 42 determines whether the heater flap opening amount 56 is less than the predetermined opening amount 106 (FIG. 4), which may be about 90%. If the heater flap opening amount 56 is less than the predetermined opening amount 106, method continues at 108. Otherwise, the method returns to 82 (FIG. 3B).

At 108, the coolant flow control module 42 receives the duct air temperature 54 from the outlet air temperature sensor 36. At 110, the temperature error module 44 calculates the error 86. At 112, the coolant flow control module 42 determines if the error 86 is less than the predetermined error 90. If the error 86 is less than the predetermined error 90, the method continues at 114. Otherwise, the method returns to 82 (FIG. 3B).

At 114, the coolant flow control module 42 controls the coolant pump 22 and/or the coolant control valve 24 to decrease the coolant flow rate F_(C) by a predetermined coolant flow rate and/or in predetermined increments 116 (FIG. 4). Each of the predetermined increments 116 may be about ¼ liter/minute. The method returns to 92.

The method continues in the secondary control mode until the heater flap opening amount 56 is greater than or equal to the predetermined heater flap opening amount 106 and/or the error 86 is greater than the predetermined error 90. For example, in FIG. 4, the coolant flow control module 42 exits the secondary control mode at 118 when the heater flap opening amount 56 is equal to the predetermined heater flap opening amount 106 and the error 86 is greater than the predetermined error 90. Although both exit conditions are met in this example, the method may exit the secondary control mode if either one of these conditions is met.

Referring to FIG. 5, a graph illustrates the effect of an example coolant flow control method according to the principles of the present disclosure on the heater flap opening amount H and the duct air temperature T_(AO). The graph includes an x-axis 130, a first y-axis 132, a second y-axis 134, a target air temperature 140, a measured duct air temperature 142, a heater flap opening amount 144, and a coolant flow rate 146. The x-axis 130 represents time in seconds. The first y-axis 132 represents the magnitude of the heater flap opening amount 144. The second y-axis 134 represents the magnitude of the coolant flow rate 146 in liters/minute.

At 148, the heater flap opening amount 144 is 100% or fully open. Between 148 and 152, the coolant flow control module 42 operates in the primary control mode by adjusting the coolant flow rate 146 to minimize the error E between the target air temperature 140 and the measured air temperature 142. At 152, the heater flap control module 46 decreases the heater flap opening amount 144 to 0% or fully closed.

Also at 152, the coolant flow control module 42 operates in the secondary control mode by decreasing the coolant flow rate 146 in predetermined increments and/or at a predetermined rate. Between 154 and 156, the coolant flow control module 42 maintains the coolant flow rate 146 at a constant value. Decreasing the coolant flow rate 146 and then maintaining the coolant flow rate 146 at a constant value allows the heater flap control module 46 to minimize the error E by adjusting the heater flap opening amount 144. Thus, as the target air temperature 140 increases, the heater flap opening amount 144 also increases. At 156, the heater flap opening amount 144 is equal to the predetermined opening amount H₁, and therefore the coolant flow control module 42 once again operates in in the primary mode by controlling the coolant flow rate 146 to minimize the error E.

The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.

Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A.

In this application, including the definitions below, the term “module” or the term “controller” may be replaced with the term “circuit.” The term “module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

The module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces that are connected to a local area network (LAN), the Internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules that are connected via interface circuits. For example, multiple modules may allow load balancing. In a further example, a server (also known as remote, or cloud) module may accomplish some functionality on behalf of a client module.

The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more modules. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more modules.

The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer.

The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may encompass a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc.

The computer programs may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation) (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. As examples only, source code may be written using syntax from languages including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK, and Python®.

None of the elements recited in the claims are intended to be a means-plus-function element within the meaning of 35 U.S.C. § 112(f) unless an element is expressly recited using the phrase “means for,” or in the case of a method claim using the phrases “operation for” or “step for.” 

What is claimed is:
 1. A system comprising: a temperature error module configured to determine an error between a target air temperature and a measured air temperature of a duct that supplies air to a cabin of a vehicle; and a coolant flow control module configured to: control a rate at which coolant flows to a heater core of the vehicle by adjusting at least one of a position of a coolant control valve of the vehicle and an output of an electric coolant pump of the vehicle; and control the coolant flow rate to decrease the error between the target air temperature and the measured air temperature.
 2. The system of claim 1 wherein the coolant flow control module is configured to determine whether to adjust the coolant flow rate to decrease the error based on at least one of an opening amount of a heater flap that regulates airflow to the heater core and a magnitude of the error.
 3. The system of claim 2 wherein the coolant flow control module is configured to adjust the coolant flow rate to decrease the error when the magnitude of the error is greater than a predetermined value.
 4. The system of claim 2 wherein the coolant flow control module is configured to adjust the coolant flow rate to decrease the error when the opening amount of the heater core is greater than a predetermined amount.
 5. The system of claim 2 wherein the coolant flow control module is configured adjust the coolant flow rate independent of the error when at least one of the opening amount of the heater flap and the magnitude of the error satisfies a predetermined criteria.
 6. The system of claim 5 wherein the coolant flow control module is configured to adjust the coolant flow rate independent of the error when the magnitude of the error is less than a predetermined value.
 7. The system of claim 5 wherein the coolant flow control module is configured to adjust the coolant flow rate independent of the error when the opening amount of the heater flap is less than a predetermined amount.
 8. The system of claim 5 wherein the coolant flow control module is configured to adjust the coolant flow rate independent of the error by decreasing the coolant flow rate at a predetermined rate.
 9. The system of claim 8 wherein the coolant flow control module is configured to stop decreasing coolant flow when at least one of: the magnitude of the error is greater than a predetermined value; and the opening amount of the heater flap is greater than a predetermined amount.
 10. The system of claim 1 wherein the coolant flow control module is configured to: determine a target flow rate based on the error, a flow rate of air passing through the duct, a temperature air in the duct, and a coolant temperature; and adjust at least one of the position of the coolant control valve and the output of the electric coolant pump to minimize a difference between the coolant flow rate and the target flow rate.
 11. A method comprising: determining an error between a target air temperature and a measured air temperature of a duct that supplies air to a cabin of a vehicle; controlling a rate at which coolant flows to a heater core of the vehicle by adjusting at least one of a position of a coolant control valve of the vehicle and an output of an electric coolant pump of the vehicle; and controlling the coolant flow rate to decrease the error between the target air temperature and the measured air temperature.
 12. The method of claim 11 further comprising determining whether to adjust the coolant flow rate to decrease the error based on at least one of an opening amount of a heater flap that regulates airflow to the heater core and a magnitude of the error.
 13. The method of claim 12 further comprising adjusting the coolant flow rate to decrease the error when the magnitude of the error is greater than a predetermined value.
 14. The method of claim 12 further comprising adjusting the coolant flow rate to decrease the error when the opening amount of the heater core is greater than a predetermined amount.
 15. The method of claim 12 further comprising adjusting the coolant flow rate independent of the error when at least one of the opening amount of the heater flap and the magnitude of the error satisfies a predetermined criteria.
 16. The method of claim 15 further comprising adjusting the coolant flow rate independent of the error when the magnitude of the error is less than a predetermined value.
 17. The method of claim 15 further comprising adjusting the coolant flow rate independent of the error when the opening amount of the heater flap is less than a predetermined amount.
 18. The method of claim 15 further comprising adjusting the coolant flow rate independent of the error by decreasing the coolant flow rate at a predetermined rate.
 19. The method of claim 18 further comprising stopping decreasing coolant flow when at least one of: the magnitude of the error is greater than a predetermined value; and the opening amount of the heater flap is greater than a predetermined amount.
 20. The method of claim 11 further comprising: determining a target flow rate based on the error, a flow rate of air passing through the duct, a temperature of air in the duct, and a coolant temperature; and adjusting at least one of the position of the coolant control valve and the output of the electric coolant pump to minimize a difference between the coolant flow rate and the target flow rate. 